Breast cancer is a disease process that impacts the life of thousands of women every year. Advances in understanding the molecular basis of the disease has been of tremendous help in the fight against breast cancer. From all the data that has been generated thus far we know that increasing the cAMP levels in breast tumor cells leads to inhibition of tumor cell proliferation. Further, cAMP levels have also been demonstrated to have an affect on multidrug resistant tumors, whereby increasing cAMP levels causes the resistant cells to be suceptable to chemotherapeutic drugs. The aim of this proposal is to understand the role of adenylyl cyclases in the regulation of transformed mamary epithelia. In addition it will also explore the potential therupuric benefit of expressing specific adenylyl cyclase isoforms in transformed and multidrug resistant cells. The proposal will also examine the molecular and biochemical aspects of the signaling pathways, in mammary epithelia, to understand the mechanisms by which interactions between the signaling pathways can be used to regulate transformation.